The present invention generally relates to a settling system for use in microcontroller-based products. More particularly, the present invention relates to an amplifier system for fast settling of an input signal, such as for high-speed, high accuracy analog to digital converters.
As the demand continues to increase for higher performance, microcontroller-based products, particularly for use in communication and processing applications, the need for improvements in the components and devices within these products also increases. This need is particularly keen in connection with analog to digital converters (xe2x80x9cADC""sxe2x80x9d), as are used, for example, to convert analog sound and video signals into digital sound and video signals respectively. Microcontroller-based products incorporating analog to digital converters include various digital devices, such as clock radios, microwave ovens, digital video recorders and the like.
While present day ADC""s are quite fast and accurate, to meet and exceed the likely demand for even higher performance electronic equipment, improvements are needed in the methods and devices which enable quick and accurate settling of the input signal to the ADC. Currently available high accuracy op-amps are generally not fast enough, and currently available high speed op-amps typically are not accurate enough to meet these needs. For example, high accuracy op-amps take a relatively long amount of time to zero in on an accurate signal level. This xe2x80x9cslow settlingxe2x80x9d can be even more evident at voltage levels greater than one volt, and many microprocessor based devices operate between one and five volts. On the other hand, high speed op-amps while generally offering xe2x80x9cfast settlingxe2x80x9d, often have a high gain error and/or offset error which reduces the accuracy of the op-amp.
Similarly, other available xe2x80x9cfast settlingxe2x80x9d devices, such as an operational transconductance amplifier (xe2x80x9cOTAxe2x80x9d) also tend to be insufficient to meet all of the anticipated design requirements. For example, because the OTA is a single stage, low gain, open-loop system, inaccuracies often obtain, even though the ADC capacitor can be quickly charged and the output signal settled quickly. Accordingly, a need exists for a system for settling the input to an ADC that addresses the ever increasing demands for fast and accurate microelectronic devices.
While the way in which the present invention addresses the above described needs will be described in greater detail hereinbelow, in general, available devices are suitably combined in an advantageous manner to facilitate both high signal settling rate as well as high accuracy signal settling. For example, in accordance with one exemplary embodiment of the present invention, a signal settling system comprises a high accuracy op-amp and a high speed OTA suitably configured to generate high speed, high accuracy signal settling. In accordance with another exemplary embodiment of the present invention, a high accuracy op-amp is configured in parallel with a high speed OTA and/or the high speed OTA is configured to be a non-linear OTA.
In accordance with another aspect of the present invention, an ADC is configured to internally facilitate both quick and accurate signal settling. In accordance with an exemplary embodiment of the present invention, an ADC comprises an internal high speed OTA configured in parallel with a connected external op-amp.